I.R. Looking through a porthole ?

[paranoid 0]

Hi all,

 

My 4 day/night cams are installed on the property and im testing them while I wait for my gv system.

 

I have a problem with 1 cam in a certain spot looking at a large garden lawn, the I.R. lights up a circle in the middle of the picture and all around the edges is blurred, this amounts to at least 50% of the cameras view.

At first I thought it was the IR camera but when I tested all 3 remaining cameras they all behaved the same, but only in this area of garden ! In all other areas the IR response is excellent, which prooves its not the camera.

 

Could it be to do with the main beam of IR hitting a patch of grass which is completely uniform and all one colour, thus confusing the cameras circuitry ?

 

I also have some extra 'standalone' Ir's and when I test them in various areas they work well but when I test them in this grassed area they are far less effective ?

 

As ever, im totally confused

 

Any comments greatly appreciated

[CCTVINSTALLER 0]

Which IR camera are you using? also what range IR does it have? ( a lot of oem, taiwanese, korean cameras overestimate their range and it is fractionally less outdoors). The distance between the camera and the lawn probably exceeds the range the IRs are capable of. What PSU are you using? You could bring the camera down so the IR can illuminate the lawn. We've learnt not to use crappy IR bullets, and a lot of people on this forum only use quality IR cams such as Extreme CCTV. If it is not a bullet, and it is in a housing such as the avtech one:

 

http://www.avtech.com.tw/english/product_34_872d.htm

 

try moving the body camera as close to the glass as possible.

[paranoid 0]

Hi,

 

The cams are these http://www.rfconcepts.co.uk/colour_sony_ir.htm

 

Im sure these are what you would call crappy cams but they are fine for this installation and the owners did not want large / medium industrial housings.

 

The effective ir range is about 100-125 feet (ive measured it) and the area of grass is about 50 feet away from the camera. The other areas are the same or much further distance and they are all fine.

 

This is why I think its a weird problem and not a straight forward one, but overall I am very very pleased with these cams.

[CCTVINSTALLER 0]

What about your PSU?, try pushing 1-2amps see if it improves IR range,

[Cooperman 0]

I.R. Looking through a porthole ?

 

paranoid,

 

A few silly questions for you.

Is the camera mounted outdoors, or looking out through glass from inside the building? If it is indoors, does the window have double glazing? Also, do you have the same lenses on every camera?

 

If you've mounted the camera to look out through a 'porthole', are you sure the IR diodes are not reflecting off the glass? Told you they were silly questions

[paranoid 0]

Thanks for the replies chaps.

 

Its nothing to do with the psu or the ir range, its strangely to do with the area / terrain. The cameras are all outside on each corner of the property and apart from one area all cams perform extremely well.

 

The other areas are all mixed terrain with trees, paths, objects etc etc. The trouble area is just one big grass lawn and i can only assume that the cameras circuitry just does not like the area been lit up by the ir.

 

As ive said before, if i move the camera anywhere else its fine with great ir range and no porthole effect. Lenses are all the same.

 

Im prepared to suffer it but thought i would mention it in case anyone else is pulling their hair out with the same weird problem.

 

Maybe the ir is somehow bouncing of the grass ? I know that sounds bizarre but what else could it be.

[VST_Man 1]

IR lighting, as focused from inside the bullet housing, is more intense, much like a flashlight, and can produce the halo effect as I call it. The rated distance, type of led, housing, plays a lot in the amount of ir light emitted. If using a more expensive camera like mentioned above you get more effiecency from the lense, lens cover, and therefore amount of ir needed becomes less. ie; a exhad beats that heck out of a CCD hands down, and add some ir to that and you get much more.

ps...I'm not expert on ir but have many years of playing with ir in the military. Use a set of ir goggles and take a look at the light pattern produced from a cheap ir camera compared to that of a decent one also. You can see the difference.

 

I'm with you in terms of what the customer needs and wants. If you explain the pros and cons of cheap and expensive and then they still want the cheap.......ok, it's on them, and you will be called back to replace those bullets sooner than later anyway.

 

I've also seen the type of lens effect the IR. I have 2 nice ir outdoor camera's with 150ft. ir capability; they came with a cheap plastic lense that produced a halo effect at night. I cleaned the lenses, replaced the rubber tubes, ect with no effect. But, once I took the lense off it was like a switch was thrown and all that smoke was gone. I finally went a started having the lenses repaed with a decent nonreflective glass lens and I have a much better pic at night.

 

Try taking off the lens cover and "lighting" it up at night. You maybe surprised at the result? If removing the lens cover improves it you either have to clean it or get a lens replacement that works better. Your local glass shop can help you out.

 

My advice; explain the pro's and con's and llow the customer to make the decision.

[Cooperman 0]

paranoid,

 

IR bouncing off the grass doesn't sound bizarre at all, that's exactly what it's doing. The chlorophyll in green leaves is highly IR reflective, so foliage in general gets lighter, and grass in particular can often appear like snow, particularly when viewed at slightly higher IR frequencies (850 - 1000nM).

 

A couple of suggestions for you. Certainly try VST_Man's idea of removing the lens cover - only thing is at the moment it's a bit damp and chilly during the night in Old London Town, so best wait until their is no frost, sleet or snow. If you do open the camera at this time of year, you'd be advised to stick a small packet of 'silica gel' inside, and that will hopefully soak up any internal damp.

 

One thing you can try without opening the camera is to reduce the IR output and see if the problem improves. If you can get hold of some very fine metal mesh (you used to be able to buy it in car spares shops, it's used for lining rust holes before applying filler!), simply cut a circle to fit the front of the camera, and then cut a small circular hole for the lens to look through.

 

Just for testing, make sure the cameras front window is clean, then tape the makeshift mesh attennuator in place, making sure the lens is not obstructed. If it works, then you can look to fit it permanantly inside the camera.

 

Another possibility is to try a small polarising filter (available from any good photographic shop) between the lens and the front glass (if there's room). this will cut down the effect of any reflections on the front 'window'.

 

Then again VST_Man may well be right about the quality of lens fitted. If the problems are caused by excessive internal reflections in the optic, the only way to get around that one, would be to change the lens for a decent one.

 

By the way, whereabouts are you in London?

[paranoid 0]

paranoid,

 

IR bouncing off the grass doesn't sound bizarre at all, that's exactly what it's doing. The chlorophyll in green leaves is highly IR reflective, so foliage in general gets lighter, and grass in particular can often appear like snow, particularly when viewed at slightly higher IR frequencies (850 - 1000nM).

 

 

Now thats what I was looking for and it goes a long way to explaining the problem. Also explains why wildlife films on the t.v. sometimes have snowy grass when filming at night.

 

Before I look at removing the lens cover im going to reposition the cam slightly so that it has other objects / foliage in view, this should lessen the porthole / glare effect as it does on the other cams.

 

Im in north london mate, dont really like to say too much more on the old information superhighway if you get my drift.

 

Cheers

[Cooperman 0]

me too, and ditto

[Cooperman 0]

Im in north london mate, dont really like to say too much more on the old information superhighway if you get my drift.

 

ah, paranoid by name and ......

[rory 0]

Firstly, I guess you are doing this, but you always have to postition IR at night, in the dark, pitch dark, use a portable monitor or small TV or something so you can see where the IR is pointing when you adjust it.

 

Infrared, requires something to reflect off. If it is an open field, or yard, it will not perform, as if there were walls on either side and at the far end of the IR's beam.

 

If you have bush, or grass and the IR is pointing on it, it can reflect, and even cause the camera's response to 'freak out'.

 

IR should be installed as low as possible, and directed as high as required, so to avoid reflection from the ground.

 

Personally I stopped Selling IR bullets for Infrared Applications, a couple years back. Now I only use Extreme CCTV if they ask for Infrared, even if it means using a cheap day night camera, coupled with an extremeCCTV Infrared bulb/LED.

Edited October 6, 2005 by Guest

[paranoid 0]

Im in north london mate, dont really like to say too much more on the old information superhighway if you get my drift.

 

ah, paranoid by name and ......

 

[paranoid 0]

Rory,

 

Thanks for that, those pictures are really very similar to this setup. The dodgy area of grass has a building behind it, much like your pool cam, and im going to raise the cam so that at least half the i.r. is on the building.

 

I would have liked to install cams / ir's like extreme or even mobotix but they are just too 'industrial' looking and my cams are pretty good for the price, overall im very impressed.

 

This forum is really handy !

 

Cheers

[rory 0]

no prob

 

yes that pool cam, I had to lower the camera and point the camera up, so the IR points towards the facing wall, that way I get an even spread of IR, pointed down on the pool/ground area does not see anything much.

 

Extreme has some nice cameras now though, they have white housings as well now. But price I would have thought would be the major issue ..whats mobotix's web site?

 

rory

 

PS ill catch it later today just going to get some zzzs, its like 6am here now ..

[Cooperman 0]

http://www.mobotix.com

 

For anyone that's interested in the U.K., they have a stand at the IIPSEC 2005 show at Stoneleigh Park (it finishes tomorrow).